You bought blackout curtains. You installed them carefully. And yet—light still leaks in from the sides, top, or center.
If this sounds familiar, you’re not alone.
Light gaps are one of the most common frustrations homeowners face after installing curtains. The good news is that the issue is rarely the fabric itself. In most cases, light leaks happen because of width, placement, or installation details that are easy to overlook.
This guide explains why light gaps happen and shows you 9 practical ways to fix them, from quick adjustments to longer-term solutions.
Why Do Curtains Still Let Light In?
Many people assume that if curtains are labeled “blackout,” they should block all light automatically. In reality, light leakage usually comes from how curtains are sized or mounted, not the fabric.
Common reasons include:
- Curtains that aren’t wide enough
- Curtain rods that stop at the window frame
- Panels that don’t overlap
- Curtains hung too low
- Flat fabric with no fullness
Where Light Gaps Usually Appear
Before fixing the problem, identify where the light is coming from:
- Side gaps – the most common issue
- Top gaps – light leaks above the rod
- Center gap – panels meet but don’t overlap
- Bottom gaps – light reflects upward from below
9 Effective Ways to Stop Light Gaps Around Curtains
1. Use Wider Curtains (The Most Effective Fix)
The most common cause of light gaps is insufficient curtain width. When curtains are too narrow, they pull flat when closed and expose the edges of the window.
As a general rule, curtains should be at least 2× the width of your curtain rod. This creates enough fabric for proper coverage and soft folds.
2. Extend the Curtain Rod Beyond the Window Frame
If your curtain rod stops right at the edge of the window, light will always find a way in. Extend the rod several inches beyond each side of the frame so the curtains can cover the edges.
- Reduces side gaps
- Improves light blocking
- Makes windows look wider and more intentional
3. Hang Curtains Higher Than the Window
Light often leaks in from the top when curtains are mounted too low. Mount the rod several inches above the window frame (or closer to the ceiling) to reduce top gaps and create a taller, more polished look.
4. Increase Curtain Fullness
Flat curtains don’t block light well. More fullness creates deeper folds, better edge coverage, and less tension pulling panels inward. If your curtains look stretched when closed, they likely need more width or additional panels.
5. Make Sure Panels Overlap in the Center
Light leaking through the middle usually means the panels just touch edge to edge. Choose wider panels and ensure several inches of overlap at the center—especially in bedrooms.
6. Choose a Header Style That Blocks Light Better
Header styles affect performance:
- Pinch pleat headers hold shape and block light more consistently
- Grommet headers can allow small gaps between rings
- Rod pocket styles sit closer to the rod and can reduce top gaps
7. Use Wraparound or Return Curtain Rods
Wraparound/return rods curve back toward the wall, preventing light from sneaking in at the sides. This hardware upgrade can dramatically reduce side gaps without changing your curtains.
8. Layer Curtains With Shades or Blinds
If you need near-total darkness, layering is highly effective. Popular combinations include blackout curtains + roller shades, or drapes + cellular shades. Layers block light from multiple angles and can improve insulation too.
9. Consider Custom Curtains for Hard-to-Fit Windows
Standard curtain sizes don’t always work for extra-wide windows, sliding glass doors, bay windows, or floor-to-ceiling installations. In these situations, custom curtains made to fit your exact window width allow you to control fullness, overlap, and coverage—eliminating light gaps at the source rather than patching the problem.
Quick Light-Gap Fix Checklist
- Are my curtains at least 2× the rod width?
- Does the rod extend beyond the window frame?
- Do the panels overlap in the center?
- Are the curtains hung high enough?
If you answered “no” to any of these, that’s likely where the light is coming from.
Frequently Asked Questions
Why do blackout curtains still let light in?
In most cases, it’s not the fabric. Curtains that are too narrow or mounted incorrectly leave gaps that allow light to pass through.
Do wider curtains really block more light?
Yes. Extra width creates fullness, which helps curtains wrap the window instead of pulling flat—reducing side and center gaps.
Can I fix light gaps without buying new curtains?
Often, yes. Extending the rod, raising the mounting height, improving overlap, or switching to wraparound/return rods can make a noticeable difference.
Are custom curtains worth it for light blocking?
For wide or unusually shaped windows, custom sizing is often the most reliable long-term solution.
